1. Field of the Invention
The invention relates to automatic performance control apparatuses which control a tempo of automatic performance in accordance with an action of a human operator such as a conductor.
2. Prior Art
Conventionally, there are provided a variety of apparatuses which control a tempo of automatic performance in real time. One type of the apparatus is known as a tapping device in which a push-button switch is turned ON responsive to a beat timing so that a tempo (i.e., beat timings) of the automatic performance is controlled in accordance with ON timing of the push-button switch. Another type of the apparatus is designed in such a way that a swing state of an object, manipulated by a human operator, is detected so as o control a tempo of the automatic performance in response to the swing state detected.
As a sensor which detects the swing state of the object described above, an acceleration sensor is generally employed. Other than the acceleration sensor, it is possible to employ a strain gauge which is attached to a conductor's baton. Herein, the strain gauge measures strain which occurs due to a swing motion of the baton, so that the swing motion is detected by the strain gauge.
The aforementioned apparatuses conventionally known suffer from problems, as follows:
The tapping device is designed to control a tempo of the automatic performance based on simple switching actions by which the push-button switch is repeatedly turned ON. However, those actions are monotonous and are far from conducting actions of the music. If the acceleration sensor is used to conduct a tune having a slow tempo, actions imparted to the acceleration sensor should be small. This causes a small variation of acceleration. Range of such a small variation of acceleration overlaps with a certain frequency range corresponding to a variation of acceleration detected by the acceleration sensor which is unintentionally swung due to an effect of gravity. For this reason, it is impossible to provide separation between those ranges. In short, it is impossible to detect a slow tempo in a stable manner. Further, even if the strain gauge is attached to the conductor's baton, fundamental function of the strain gauge is similar to that of the acceleration sensor. So, as similar to the case of the acceleration sensor, the strain gauge cannot detect slow acceleration and slow deceleration as well as uniform motion applied to the baton.
The conventional apparatuses are fundamentally designed to control a tempo of the automatic performance by designating beat timings. So, there is a possibility that some cause produce a deviation between an action of a performer and a beat timing of performance. For example, although the performer intends to make a swing action with respect to a second beat in certain time, the performance may be mistakenly made with respect to a first beat. If such a deviation occurs, it is difficult to restore such a deviated state to an original state of the performance.